1. Field of the Invention
The invention relates to a method for operating a lamp having a first light emitting means for direct light and a second light emitting means for the indirect illumination of an object. The lamp has a controller to separately control the first light emitting means and the second light emitting means, as well as a light sensor for detecting the total amount of light in the range of the light sensor including any existing extraneous light there. The light sensor connected to the controller.
2. Background of the Invention
The current state of knowledge is as follows.
Such a method is disclosed, for example in DE 10 2009 016 753 A1. In that case, one or more free-standing lamps are provided for room lighting, and are formed either individually or in their entirety to emit a first indirect light component, a second large-area direct light component illuminating a designated object, as well as a third light component that is essentially directly bundled. In this case, the first light component is controlled centrally, while the third light component may be switched on and off by a user. It is so arranged that the light component output of the lamps that is used for room related lighting is controlled centrally, while, on the other hand, the light component used for specific local lighting is adjustable by a user.
Another method for operating a lamp is known from DE 10 2010 031 428 A1. The lamp has a first light source to produce general lighting and a control unit by means of which the first light source emits light at various intensities with respect to a set brightness level. The light has a sensor for detecting a brightness level. The control unit controls the first light source as a function of the brightness level value detected by the light sensor. In addition, the lamp has a second light source to produce a direct light oriented, for example, towards a work surface. This second light source may be moved between a first and a second switching state, in particular switched on and off. The control unit is so designed that the above-mentioned brightness level is altered by changing the switching state of the second light source. In such a method, the second light source may only be switched on and off. There is no brightness control of this second light source.
Furthermore, combined lamps are known, especially workstation or freestanding lamps that provide direct lighting of a specific object such as a workstation through a first lighting means, and indirect lighting, for example of a ceiling, through a second lighting means. Such lamps may be adjusted by a sensor depending on the brightness of the light. Such lamps are used in a sensor system for presence detection, so if someone approaches the lamp, these lamps may switch on automatically.
The problem with such lamps that are switched on through presence detection is that they may be unintentionally and immediately switched off in adverse lighting situations. Such an unfavorable lighting situation may, for example, occur if the incident amount of light is minimal at the light sensor and undershoots the switch-on value, while the indirect illumination provides too high a feedback value to the light sensor. In this situation, the switch-off value is then undershot and the lamp is switched off. This phenomenon is known as a yo-yo effect, and should be avoided in lamps.
Another problematic lighting situation arises when the light component from the second light emitting means reaching the sensor is very high because of the conditions in the room in which the lamp is located. This problem of the unwanted influence of the various light components remains unresolved.
This is where the present invention is applied.
The present invention aims to provide a method for operating a lamp of the kind mentioned, i.e. a lamp having a separately controllable first light emitting means to provide a direct light source, along with further light emitting means to provide an indirect light component, whereby the above-mentioned disadvantages may be avoided by means of the invented control system.
The object of the present invention is to resolve the problems mentioned above.